On the first 3 tests of her chemistry class, Umaima got an average score of 77. What does she need on the next test to have an overall average of 82?
Let her score on the next test be $x$ The sum of all of her scores is then $3 \cdot 77 + x$ The same sum must also be equal to $4 \cdot 82$ Solve: $x = 4 \cdot 82 - 3 \cdot 77 = 97$.